JPH10301391A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniformalize a layer thickness of non-magnetic toner on the toner carrier, and obtain an excellent visual image with uniform density by providing an outside magnet on a position parting from a layer thickness control blade, and flatting warp and undulation of a layer thickness controlling blade by the magnetic force of the magnet. SOLUTION: This developing device is provided with the outside magnet 19 at the position parting from the layer thickness controlling blade 13, on the position above a free end side 18 of the layer thickness controlling blade 13. The layer thickness controlling blade 13 composed of a magnetic material is attracted by the magnetic force by the outside magnet 19, over almost its full length. Thus, the warping deformation of the layer thickness controlling blade 13 is straightened, and the free end side 18 of the layer thickness controlling blade 13, over full length thereof is almost uniformly held in press contact with the surface of the developing roller 7. Accordingly, dispensed with increasing a shape accuracy of the layer thickness controlling blade 13, the fitting accuracy thereof, or the accuracy of the fitting section thereof, the blade is made possible to be held in press contact with the surface of the developing roller 7 across the toner, by uniform pressure over its full length in the length direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a toner carrier which is driven to rotate, and a thickness regulating blade which regulates the thickness of the non-magnetic toner carried and conveyed on the surface of the toner carrier. The layer thickness regulating blade is in pressure contact with the surface of the toner carrier via the non-magnetic toner, and the electrostatic force formed on the latent image carrier by the non-magnetic toner whose layer thickness is regulated by the layer thickness regulating blade. The present invention relates to a developing device that visualizes a latent image as a toner image.

[0002]

2. Description of the Related Art In an image forming apparatus such as an electronic copier, a printer, a facsimile, or a multifunction machine having at least two of these functions, a powdery material to which an auxiliary agent is externally added if necessary. It is conventionally well known to employ a developing device of the above type using a non-magnetic toner, that is, a non-magnetic one-component developer.

A developing device of this type can simplify the maintenance of the device and reduce the size of the device as compared with a developing device using a two-component developer having a carrier in addition to the toner. In addition, since a non-magnetic toner is used, a clear image can be obtained even when a color (chromatic) image is formed.

In this type of developing device, the layer thickness of the non-magnetic toner is regulated by a layer-thickness regulating blade, and the electrostatic latent image is visualized by the regulated non-magnetic toner. Due to errors or variations in the shape accuracy of the layer thickness regulating blade, its mounting accuracy, or the accuracy of its mounting portion, the layer thickness regulating blade is deformed. Cannot be pressed against the surface of the non-magnetic toner with a uniform pressure, and thus the layer thickness of the non-magnetic toner after passing through the layer thickness regulating blade becomes uneven. When a visible image is formed with such a toner, density unevenness occurs in the image. Further, in a portion where the layer thickness regulating blade is excessively pressed against the surface of the toner carrier, non-magnetic toner cannot pass therethrough, and a streak in which the toner does not ride on the toner layer after passing the layer thickness regulating blade occurs. The image quality of the visible image formed by the non-magnetic toner is streaked, and the image quality is significantly deteriorated. Further, if there is a portion where an excessive amount of toner adheres to the surface of the toner carrier, the toner may be scattered.

For this reason, it is necessary to improve the shape accuracy of the layer thickness regulating blade and the mounting accuracy of the mounting portion thereof so that the layer thickness regulating blade can be uniformly pressed against the surface of the toner carrier via the toner. It is not easy to configure the developing device in such a manner, and a large cost is required.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned conventional disadvantages and to make the contact pressure of the layer thickness regulating blade against the surface of the toner carrier uniform with a simple structure. Accordingly, it is an object of the present invention to provide a developing device capable of forming a high-quality visible image for a long time.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a developing device of the type described at the beginning.
The layer-thickness regulating blade is made of a magnetic material, and the layer-thickness regulating blade is provided with an external magnet on the side opposite to the side where the toner carrier is located, the magnet being separated from the layer-thickness regulating blade. A developing device is proposed (claim 1).

In this case, it is advantageous that the toner carrier has on its surface a plurality of magnetic poles having alternately different polarities along the moving direction of the surface (claim 2).

Further, in the developing device according to claim 1 or 2, the external magnet is constituted as a rotating body driven to rotate, and the rotating body is alternately provided on a surface thereof along a moving direction of the surface. It is advantageous to have a plurality of magnetic poles with different polarities (claim 3).

Further, in the developing device according to any one of claims 1 to 3, it is advantageous that the external magnet is movably supported so as to be able to approach or separate from the layer thickness regulating blade. (Claim 4).

Further, in the developing device according to any one of claims 1 to 4, it is advantageous that the external magnet is an electromagnet (claim 5).

Further, in the developing device according to any one of claims 1 to 5, the layer thickness regulating blade has a surface facing the toner carrier and a surface facing the external magnet. Advantageously, it is constructed as permanent magnets having respective magnetic poles of different polarities (claim 6).

Further, in the developing device according to any one of claims 1 to 6, magnetic poles having different polarities are provided on a surface facing the toner carrier and a surface facing the external magnet. It is advantageous if the permanent magnets respectively provided are mounted on the layer thickness regulating blade (claim 7).

Further, the developing device according to claim 7 may be configured to include a layer thickness regulating blade made of a non-magnetic material in place of the layer thickness regulating blade made of a magnetic material (claim 8). .

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings, and the above-mentioned conventional disadvantages will be more specifically clarified with reference to the drawings.

In FIG. 1, a belt-shaped photoreceptor 1, which is an example of a latent image carrier, is wound around rollers 2 and 3 and other rollers (not shown) and is driven to rotate in the direction of arrow P. At this time, an electrostatic latent image is formed on the surface of the photoconductor.
A developing device 15 is provided to face the surface of the photoreceptor 1, and the toner container 4 of the developing device 15 contains a powdered non-magnetic toner T to which an auxiliary agent is externally added as necessary. The non-magnetic toner T is circulated while being stirred by the agitator 6 rotating in the toner container 4. A developing roller 7 partially exposed from the toner container 4 is rotatably supported on front and rear side plates of the toner container 4.
The developing roller 7 is rotated counterclockwise in FIG. 1 to face the surface of the photoconductor 1. Further, a toner supply roller 8 is provided in contact with the developing roller 7, and this toner supply roller 8 is also rotatably supported by the front and rear side plates of the toner container 4 and is driven to rotate counterclockwise in FIG.

The developing roller 7 constitutes an example of a toner carrier which carries and transports the non-magnetic toner T on its surface. The developing roller 7 is made of, for example, a conductor including the central rotating shaft 5. It has a roller body 9 and an outer layer 10 made of an insulator or a dielectric or a substance having a medium resistance (10 ^{6 to} 10 ¹⁰ Ωcm) integrally laminated on the outer peripheral surface thereof.
The outer layer 10 is made of, for example, a synthetic resin or rubber, and a coating layer may be formed on the surface of the outer layer 10 in order to adjust a coefficient of friction or a resistance value with respect to the toner or to suppress formation of toner filming. Such a developing roller 7
Extend in the width direction of the photoconductor 1.

The toner supply roller 8 has a conductive central shaft 11 and an outer layer 12 laminated therearound.
The outer layer 12 is formed of a sponge or the like capable of increasing the coefficient of friction with respect to toner and increasing the contact area with the developing roller 7.

The non-magnetic toner T in the toner container 4 is conveyed to the toner supply roller 8 by the agitator 6, and then supplied to the surface of the developing roller 7 by the toner supply roller 8. During this series of operations, the non-magnetic toner T is frictionally charged to a predetermined polarity, for example, positive, and the surfaces of the toner supply roller 8 and the developing roller 7 are charged to the opposite polarity. In this way, the nonmagnetic toner T is electrostatically carried on the surfaces of the toner supply roller 8 and the developing roller 7, and is conveyed by its rotation. A bias voltage is applied to each of the toner supply roller 8 and the developing roller 7, and a potential is provided between the developing roller 7 and the toner supply roller 8. Transfer to the surface of No. 7.

The non-magnetic toner T carried on the surface of the developing roller 7 is conveyed in the direction of rotation by the rotation of the developing roller 7, and then its layer thickness is regulated by a layer thickness regulating blade 13. At this time, the amount of charge of the nonmagnetic toner T is increased by frictional contact with the layer thickness regulating blade 13.

The non-magnetic toner T on the developing roller 7 that has passed through the layer thickness regulating blade 13 is carried to the developing area 14 where the developing roller 7 and the photosensitive member 1 are opposed to each other. This is used for visualizing the formed electrostatic latent image. The photoconductor 1 is made of, for example, an optical semiconductor, and the charged toner on the developing roller 7 is electrostatically transferred to the electrostatic latent image formed by the charge holding unit on the surface, and the electrostatic latent image is transferred to the toner. It is visualized as an image. Although this is an example of regular development, the electrostatic latent image can be visualized by reversal development. Further, in the example shown in FIG. 1, the developing roller 7 is in contact with the photoreceptor 1 via the toner. However, these may be slightly separated from each other to perform non-contact development.

The non-magnetic toner T that has not passed through the developing area 14 and is not used for development is returned to the toner supply roller 8 while being carried on the developing roller 7. The toner image formed on the surface of the photoreceptor 1 is transferred to a transfer material (not shown), for example, a transfer sheet, and the transferred toner image is fixed on the transfer sheet by a fixing device (not shown). The toner remaining on the surface of the photoconductor after the transfer of the toner image is removed from the surface of the photoconductor by a cleaning device (not shown).

As described above, the illustrated developing device 15
Developing roller 7 which is an example of a rotatable toner carrier
And a layer thickness regulating blade 13 for regulating the layer thickness of the non-magnetic toner T carried and conveyed on the surface of the toner carrier, and the layer thickness regulating blade 13 It is pressed against the surface of the carrier. The electrostatic latent image formed on the photoconductor 1 as an example of the latent image carrier is visualized as a toner image by the non-magnetic toner whose layer thickness is regulated by the layer thickness regulating blade 13.
It is also possible to use a drum-shaped latent image carrier or a toner carrier composed of an endless belt that is driven to rotate.

FIG. 2 is a schematic plan view of the layer thickness regulating blade 13 and the toner container 4 as viewed from above. As can be seen from FIG. 2 and FIG. 1, the layer thickness regulating blade 13 has, for example, a predetermined elasticity. A holder 16 which is made of a thin plate and extends in the axial direction of the developing roller 7 and has a high rigidity is joined to a base end in the width direction. The thickness of the layer thickness regulating blade 13 is, for example, about 0.1 mm to 1 mm.
The holder 16 and the layer thickness regulating blade 13 are fixed to the upper wall of the toner container 4 by screws 17 at respective ends in the longitudinal direction. The free end side 18 in the width direction of the layer thickness regulating blade 13 is pressed against the surface of the developing roller 7 via the toner.

The layer thickness regulating blade 13 of this embodiment is made of a magnetic material, such as SUS420, as will be described later, but its material, shape, thickness, and contact state with the developing roller 7 are formed on the photosensitive member 1. Is set in accordance with the quality required for the toner image to be formed. That is, the developing roller 7
Since the quality of the toner image is affected by characteristics such as the layer thickness of the non-magnetic toner and the amount of charge thereof, the material of the layer thickness regulating blade 13 is set in consideration of these factors.

The configuration itself of the developing device 15 described above is as follows.
There is no difference from the conventional developing device. In such a conventional developing device, as described above, the layer thickness regulating blade 1
It is difficult to evenly contact the surface of the developing roller 7 with the surface of the developing roller 7, and as shown in an exaggerated manner in FIG.
3 may undulate or warp in a wavy state in the longitudinal direction. The layer thickness of the nonmagnetic toner that has passed through such a layer thickness regulating blade 13 is
The unevenness occurs in accordance with the undulation state, and density unevenness occurs in the toner image formed by the non-magnetic toner.
Further, the toner may be scattered from a portion where a large amount of non-magnetic toner adheres to the developing roller. Further, as shown in FIG. 15, the toner T is applied to a portion where the layer thickness regulating blade 13 excessively hits the surface of the developing roller 7.
As shown in FIG. 16, toner-free streaks L are formed in the toner layer after passing through the layer-thickness regulating blade, as shown in FIG. Deteriorates. Note that the hatched lines in FIG. 16 indicate the toner T on the developing roller 7.

The layer thickness regulating blade 13 shown in FIG. 1 has its base end fixed to a holder 16 having high rigidity. However, it is not possible to prevent the layer thickness regulating blade 13 from undulating with this structure alone. Have difficulty. Further, a large number of screws 17 shown in FIG. 2 are provided not only at each end of the layer thickness regulating blade 13 but also in the longitudinal direction thereof, and the layer thickness regulating blade 13 is firmly fixed to the toner container 4 so that the layer thickness regulating blade 13 is fixed. Although it is conceivable to prevent the undulation of the blade 13, in this case, only the layer-thickness regulating blade portion fixed by the screw is firmly fixed to the toner container 4. Is remarkable.

For this reason, conventionally, it has been necessary to improve the shape accuracy of the layer thickness regulating blade 13 and the attachment accuracy of the attachment portion to the toner container. Not only can not be completely prevented, but adopting this configuration requires a great deal of cost.

Therefore, in the developing device 15 of this embodiment,
The thickness regulating blade 13 is made of a magnetic material as described above, and as shown in FIG.
3, on the side opposite to the side on which the toner carrier composed of the developing roller 7 is located, that is, above the free end side 18 of the layer thickness regulating blade 13 in the example shown in FIG.
An external magnet 19 is provided at a distance from the external magnet 3. The external magnet 19 is provided at a position opposed to the layer thickness regulating blade portion pressed against the toner carrier via the toner. Here, "external" in this external magnet
The wording indicates that the magnet 19 is separated from the layer thickness regulating blade 13 and is arranged outside the layer thickness regulating blade 13, and a permanent magnet 20 (see FIG. 12, FIG. 13).

The external magnet 19 shown in FIG. 1 extends long along the thickness regulating blade 13 and
3 extends over the entire length or almost the entire length thereof, and is located parallel to the developing roller 7. Such an external magnet 1
The surface 19B on the side facing the layer thickness regulating blade 13 and the surface 19B on the opposite side are fixed to the mounting portion 21 of the image forming apparatus main body. The surface 19A of the external magnet 19 on the side facing the layer thickness regulating blade 13 is the N pole, and the surface 1A on the opposite side is
Although 9B has an S pole, its magnetized state may be reversed, and the surface 19A may be an S pole and the opposite surface 19B may be an N pole. Each magnetic pole extends along the entire length of the external magnet 19 along its length.

According to the above-described configuration, the thickness regulating blade 13 made of a magnetic material is pulled by the magnetic force of the external magnet 19 over substantially the entire length thereof. Therefore, the undulation of the layer thickness regulating blade 13 is corrected, and the free end side 18 of the layer thickness regulating blade 13 can be brought into substantially uniform pressure contact with the surface of the developing roller 7 over its entire length. Even if the shape accuracy of the layer thickness regulating blade 13, the mounting accuracy thereof, or the accuracy of the mounting portion is not increased as in the related art, the swelling and warpage of the layer thickness regulating blade is corrected, and the uniformity is obtained over the entire length in the longitudinal direction. By pressure, the layer thickness regulating blade 13 is
Thus, the toner can be pressed against the surface of the developing roller 7 via the toner.

In this example, since the layer thickness regulating blade 13 is attracted by the external magnet 19, the layer thickness of the non-magnetic toner after passing through the layer thickness regulating blade 13 is thicker than when the external magnet 19 is not provided. The thickness of the developing roller 7
This makes the density of the toner image formed on the photoreceptor 1 uniform, and further prevents the toner image from being streaked without toner.
The image quality of the toner image can be improved.

In the developing device 15, since the non-magnetic toner T is used as a developer, the external magnet 19
Is provided, there is no adverse effect on the toner, and a high-quality toner image can always be formed.

FIG. 3 shows three positions in the longitudinal direction of the developing roller 7 when the magnetic force of the external magnet 19 is changed, that is, FIG.
4 shows how the amount of nonmagnetic toner per unit area (mg / cm ² ) changes on the right side A, the left side B, and the center C shown in FIG. Is the central C,
“△” indicates the toner amount on the left side B, and “○” indicates the toner amount on the right side A. As can be seen from this figure, when the magnetic force is zero, that is, when the external magnet 19 is not provided, the amount of toner attached to each of the portions A, B, and C in the axial direction of the developing roller 7 greatly varies, and the thickness of the toner layer is large. Are non-uniform. On the other hand, when the external magnet 19 is provided and its magnetic force is set particularly to 0.5 T (Tessler) or more, the influence of the magnetic force on the layer thickness regulating blade 13 increases,
The contact pressure of the blade 13 against the developing roller 7 is made uniform over the longitudinal direction of the developing roller 7,
, The amount of non-magnetic toner, that is, the thickness of the toner layer becomes substantially uniform.

Further, in the configuration shown in FIGS. 1 and 2 and described above, the toner carrier comprising the developing roller 7 is provided with a surface having different polarities alternately along the moving direction of the surface. It can also be configured to have a plurality of magnetic poles. For example, as shown in FIG. 4 to FIG. 7, a large number of magnetic poles extending in the longitudinal direction are provided on the surface of the developing roller 7 all around the circumference thereof. The polarity of the magnetic pole is alternately changed in the circumferential direction of the developing roller 7. For example, the outer layer 10 of the developing roller 7 is made of a material in which a polymer material and a magnetic powder are mixed, and the surface thereof is magnetized to form magnetic poles having the same pitch of the S pole and the N pole on the surface.

As described above, when the developing roller 7 rotates counterclockwise in FIG. 1, the magnetic pole (N pole or S pole) of the developing roller 7 When the layer reaches the portion of the layer thickness regulating blade 13 pressed against the developing roller 7 via, the magnetic force acting on the layer thickness regulating blade 13 increases, and the layer thickness regulating blade 13 strongly contacts the surface of the developing roller 7. On the other hand, when the portion between the magnetic poles of the developing roller 7 reaches the layer thickness regulating blade 13 as shown in FIG. 6, the magnetic force acting on the layer thickness regulating blade 13 is weakened, and the pressure contact force on the developing roller is small. Become. That is, during the rotation of the developing roller 7, the contact force of the layer thickness regulating blade 13 on the developing roller 7 fluctuates with the period of the pitch of the magnetic poles, and the layer thickness regulating blade 13 generates a slight vibration.

In addition, since the magnetic force of the external magnet 19 (FIG. 1) also acts on the thickness regulating blade 13, the external magnet 1
In the case where the magnetic pole of the surface 19A facing the layer thickness regulating blade 13 of FIG. 9 is the N pole, the magnetization state of the layer thickness regulating blade 13 with the rotation of the developing roller 7 and the external magnet 19, the layer thickness regulating blade 13 and The inquiring and repelling states of the developing roller 7 are as shown in Table 1 below.

[0038]

[Table 1]

In Table 1, (I) shows the case where the magnetic force of the external magnet 19 is set to be smaller than the magnetic force of the developing roller 7 (external magnet <developing roller). This is a case where the magnetic force is set to be larger than the magnetic force of the developing roller 7 (external magnet> developing roller). The “outside” of the magnetization state of the layer thickness regulating blade indicates the magnetization state of the surface of the layer thickness regulating blade 13 on the side facing the external magnet 19, and the “inside” similarly indicates the layer on the side facing the developing roller 7. 4 shows a magnetization state of a thickness regulating blade surface. Further, “→ ←” indicates that they attract each other, and “← →” indicates that they repel each other.

According to Table 1, when the magnetic force of the external magnet 19 is smaller than the magnetic force of the developing roller 7, when the N pole of the developing roller 7 faces the layer thickness regulating blade 13 (the state of FIG. 5),
The developing roller 7 and the layer-thickness regulating blade 13 attract each other, and the external magnet 19 and the layer-thickness regulating blade 13 repel each other, whereby the pressure contact force of the layer-thickness regulating blade 13 against the developing roller 7 increases. Conversely, when the magnetic force of the external magnet 19 is larger than the magnetic force of the developing roller 7, when the N pole of the developing roller 7 faces the layer thickness regulating blade 13, the developing roller 7 and the layer thickness regulating blade 13 repel, and the external magnet 19 And the layer thickness regulating blade 13 attracts each other, whereby the pressing force of the layer thickness regulating blade 13 against the developing roller 7 becomes weak.

As described above, when the external magnet 19 is provided, when the developing roller 7 is magnetized as shown in FIG. 4, the thickness regulating blade 13 has a larger amplitude than when the external magnet 19 is not provided. Vibrate. As a result, the non-magnetic toner can be effectively loosened with a relatively large amplitude vibration at the contact portion between the layer thickness regulating blade 13 and the developing roller 7, and as shown in FIG. Can be prevented from being clogged between the layer thickness regulating blade 13 and the developing roller 7 and agglomerating. As a result, it is possible to more effectively prevent a defect in which a streak in which the toner does not exist is present in the toner image.

When the developing roller 17 is not provided with a magnetic pole, the amplitude of the vibration of the layer thickness regulating blade 13 is as shown in FIG.
Is small enough to neglect the amount by which the external magnet 19 pulls the layer thickness regulating blade 13 to displace it.

Next, in each of the above-described configurations, instead of fixing the external magnet 19 to the image forming apparatus main body immovably, FIG.
As shown in FIG.
It can also be configured as That is, this rotating body 2
The second central shaft 23 is rotatably supported by the image forming apparatus main body, and is configured to be rotationally driven, for example, in a counterclockwise direction in FIG. 8 by a driving device (not shown). The rotator 22 is configured so as to have a plurality of magnetic poles on its surface which have alternately different polarities along the moving direction of the surface. As in the case of the developing roller 7 shown in FIG. 4, a large number of magnetic poles of equal pitch are provided in the circumferential direction on the surface of the rotating body 22, and the polarity of the magnetic pole (S
(Pole, north pole) alternately. Each magnetic pole in this case also extends in the axial direction of the rotating body 22.

As described above, the external magnet 19 is configured as the rotating body 22 that is driven to rotate, and the rotating body 22 is driven to rotate during the developing operation. Similarly, the non-magnetic toner can be loosened by vibrating the layer thickness regulating blade 13 made of a magnetic material, and the clogging phenomenon can be prevented. In addition, as in the embodiment shown in FIGS. 4 to 7, if only the developing roller 7 is magnetized, the layer thickness regulating blade 13 is controlled by the rotation speed of the developing roller 7.
The frequency of the magnetic force acting on the
In the embodiment shown in FIG. 8, by appropriately setting the rotation speed of the rotating body 22, the layer thickness regulating blade 13
Can be changed substantially freely. Therefore, for example, the clogging phenomenon of the non-magnetic toner can be more effectively prevented by increasing the frequency.

The configuration shown in FIG. 8 can be applied to all of the developing devices shown in FIGS.

In each of the above-described configurations, the external magnet 19 can be movably supported so that it can approach or separate from the layer thickness regulating blade 13. For example, as shown in FIG.
The external magnet 19 is movably supported along a guide 24 on the side of the image forming apparatus main body so that the external magnet 19 can move in a direction perpendicular to the surface 3.

By moving the external magnet 19 with respect to the layer thickness regulating blade 13, the distance between the external magnet 19 and the layer thickness regulating blade 13 can be changed. Can be adjusted freely. As a result, a magnetic force having a strength corresponding to the characteristics of the non-magnetic toner, for example, the fluidity thereof is applied to the layer thickness regulating blade 13 to form a uniform toner layer having an optimum thickness on the developing roller. Can be. Further, since the thickness of the toner layer on the developing roller 7, that is, the amount of toner per unit area can be controlled by adjusting the magnetic force, it is possible to adjust the density of the toner image.

The external magnet 19 can be manually adjusted and moved. In addition, the external magnet 19 can be moved by a driving device not shown in FIG. 9, for example, a motor or a solenoid.

The configuration shown in FIG. 9 is also applicable to all the configurations shown in FIGS.

In each of the configurations described above, when the external magnet 19 is formed by an electromagnet, the strength of the magnetic force acting on the layer thickness regulating blade 13 made of a magnetic material is controlled by controlling the current value supplied to the coil. You can change it freely. As a result, a toner layer having an optimum thickness can be easily formed, or the density of the toner image can be freely adjusted. The configuration using this electromagnet is also shown in FIG.
9 is applicable, and the rotator 22 shown in FIG. 8 can be constituted by an electromagnet. In particular, when the external magnet 19 of each constitution except for FIG. 8 is constituted by an electromagnet. , When an alternating current is supplied to the coil,
Since the polarity of the magnetic pole on the surface of the electromagnet facing the layer thickness regulating blade 13 changes alternately, the layer thickness regulating blade 13 is vibrated to effect the non-magnetic toner T in the same manner as in the embodiment shown in FIG. The problem that the toner image is loosened and streaks can be eliminated.

In each of the above-described configurations, the layer thickness regulating blade 13 as schematically shown in FIGS. 10 and 11 may be constituted by a permanent magnet. In the example shown in FIG. 10, the surface of the layer thickness regulating blade facing the developing roller 7 is magnetized to the S pole, the surface of the layer thickness regulating blade facing the external magnet 19 is magnetized to the N pole, The surface 19A of the external magnet 19 on the side facing the layer thickness regulating blade 13 is an N pole. Thus, the external magnet 19 and the layer thickness regulating blade 13
If the surfaces facing each other have the same polarity, a repulsive force is generated between them, and the layer thickness regulating blade 13 is strongly pressed against the surface of the developing roller 7. On the other hand, in the example shown in FIG. 11, the layer thickness regulating blade 1 on the side facing the developing roller 7
The surface of No. 3 is magnetized to the N pole, the opposite surface is magnetized to the S pole, and the surface 19A of the external magnet 19 is magnetized to the N pole. As described above, when the opposing surfaces of the external magnet 19 and the layer-thickness regulating blade 13 have opposite polarities, a pulling force is generated therebetween, and the layer-thickness regulating blade 13 receives a force in a direction away from the developing roller 7. , Layer thickness regulating blade 1
The force with which the roller 3 is pressed against the developing roller 7 is reduced.

As described above, by appropriately selecting the polarity of the magnetic pole on each surface of the layer thickness regulating blade 13 and the polarity of the magnetic pole on the surface 19A of the external magnet 19, the layer thickness regulating blade 13 can be moved relative to the developing roller 7. Pressing or releasing force can be applied, but in any case, the layer thickness regulating blade 13
Can be pressed against the developing roller 7 with a substantially uniform pressure over the entire length in the longitudinal direction, whereby the thickness of the toner layer can be made uniform and the density unevenness of the toner image can be prevented. Prevention can be achieved.

By selecting the polarity of each magnetic pole, the thickness of the toner layer on the developing roller can be adjusted.
This makes it possible to set a desired density of the toner image in a wide range.

The configurations shown in FIGS. 10 and 11 are also applicable to all the configurations shown in FIGS.

As described above, the developing device of the embodiment shown in FIGS.
Are configured as permanent magnets having magnetic poles having polarities different from each other on the surface facing the developing roller 7 and the surface facing the external magnet 19, which are examples of the toner carrier. In the embodiment shown in FIG. 13, the permanent magnet 20 shown briefly above is attached to the surface of the layer thickness regulating blade 13 facing the external magnet 19 by, for example, bonding. The permanent magnet 20 has a surface facing the toner carrier including the developing roller 7 and the external magnet 1.
On the surface facing the side 9, there are magnetic poles having different polarities from each other. 10 and FIG.
The same functions and effects as those of the developing device shown in FIG. Layer thickness regulating blade 1 shown in FIGS. 10 to 13
Each magnetic pole of the permanent magnet 20 extends long in the longitudinal direction of the thickness regulating blade 13.

The configuration shown in FIGS. 12 and 13 can also be applied to all the configurations shown in FIGS. 1 to 11, but in the embodiment shown in FIGS. Instead of the layer thickness regulating blade, a layer thickness regulating blade 13 made of a non-magnetic material can be used.

[0057]

According to the first aspect of the present invention, since the undulation and warpage of the layer thickness regulating blade can be corrected by the magnetic force of the external magnet, the layer thickness of the non-magnetic toner on the toner carrier can be made uniform. Thus, a high-quality visible image having a uniform density can be formed.

According to the developing device of the present invention, the layer thickness regulating blade can be finely vibrated, the clogging phenomenon of the non-magnetic toner can be prevented, and the streaking of the visible image can be prevented. The image quality can be improved.

According to the third aspect of the present invention, the layer thickness regulating blade can be finely vibrated, the non-magnetic toner can be prevented from clogging, and the streaking of a visible image can be prevented. The image quality can be improved. In addition, the frequency of the magnetic force acting on the layer thickness regulating blade can be adjusted by changing the number of revolutions of the rotating body constituting the external magnet.

According to the fourth aspect of the invention, the magnetic force acting on the layer thickness regulating blade can be changed to form a toner layer having an optimum thickness, and the density of the toner image can be adjusted by adjusting the magnetic force. It is also possible to do.

According to the developing device of the fifth aspect, by controlling the value of the current supplied to the electromagnet constituting the external magnet, the magnetic force acting on the layer thickness regulating blade can be changed very easily, and the optimum value can be obtained. It is possible to form a toner layer having an appropriate thickness, and it is also possible to adjust the density of the toner image by adjusting the magnetic force.

According to the present invention, the pressure applied by the layer thickness regulating blade to the non-magnetic toner on the toner carrier can be set in a wide range, and the visible image can be easily formed. It is possible to make the concentration uniform.

[Brief description of the drawings]

FIG. 1 is a sectional view of a developing device according to an embodiment of the present invention.

FIG. 2 is a schematic plan view showing a part of the developing device shown in FIG.

FIG. 3 is a graph showing that a toner layer on a developing roller can be made uniform by providing an external magnet.

FIG. 4 is a perspective view showing a developing roller having a large number of magnetic poles on a peripheral surface.

FIG. 5 is an explanatory diagram showing that a magnetic force of a developing roller increases a pressing force of a layer thickness regulating blade against the developing roller.

FIG. 6 is an explanatory view showing that the magnetic force of the developing roller makes the pressure contact force of the layer thickness regulating blade against the developing roller weaker than in FIG.

FIG. 7 is an explanatory diagram showing that a magnetic force of a developing roller increases a pressing force of a layer thickness regulating blade against the developing roller.

FIG. 8 is a sectional view of a developing device in which an external magnet is constituted by a rotating body.

FIG. 9 is a cross-sectional view of the developing device in which an external magnet is movably supported.

FIG. 10 is an explanatory diagram illustrating a developing device in which a layer thickness regulating blade is configured by a permanent magnet.

FIG. 11 is an explanatory view showing a developing device in which a layer thickness regulating blade is constituted by a permanent magnet.

FIG. 12 is an explanatory view showing a developing device in which a permanent magnet is attached to a layer thickness regulating blade.

FIG. 13 is an explanatory diagram showing a developing device in which a permanent magnet is attached to a layer thickness regulating blade.

FIG. 14 is an explanatory view showing that the layer thickness regulating blade of the conventional developing device has undulated.

FIG. 15 is an explanatory diagram showing a state in which toner is clogged and aggregated between a layer thickness regulating blade and a developing roller of a conventional developing device.

FIG. 16 is an explanatory view showing a state in which streaks are formed on a toner layer on a developing roller of a conventional developing device.

[Explanation of symbols]

 13 Layer thickness regulating blade 15 Developing device 19 External magnet 20 Permanent magnet 22 Rotating body T Toner

 ────────────────────────────────────────────────── ─── Continued from the front page (72) Inventor Takayuki Yoshii 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company, Ltd.

Claims (8)

[Claims] An image forming apparatus comprising: a toner carrier that is driven to rotate; and a layer thickness regulating blade that regulates a layer thickness of nonmagnetic toner carried and conveyed on the surface of the toner carrier. Is pressed against the surface of the toner carrier via the non-magnetic toner, and the electrostatic latent image formed on the latent image carrier is formed as a toner image by the non-magnetic toner whose layer thickness is regulated by the layer thickness regulating blade. In the developing device for visualizing, the layer thickness regulating blade is made of a magnetic material,
The developing device according to claim 1, wherein an external magnet is provided on the side opposite to the side on which the toner carrying member is located with respect to the layer thickness regulating blade. 2. The developing device according to claim 1, wherein the toner carrier has a plurality of magnetic poles having different polarities on a surface thereof alternately along a moving direction of the surface. 3. The external magnet is configured as a rotating body that is driven to rotate, and the rotating body has a plurality of magnetic poles on a surface thereof having alternately different polarities along a moving direction of the surface. The developing device according to claim 1, wherein 4. The developing device according to claim 1, wherein the external magnet is movably supported so as to be able to approach or separate from the layer thickness regulating blade. 5. The external magnet according to claim 1, wherein said external magnet comprises an electromagnet.
5. The developing device according to any one of claims 1 to 4. 6. The layer thickness regulating blade is configured as a permanent magnet having magnetic poles having polarities different from each other on a surface facing the toner carrier and a surface facing the external magnet. 6. The developing device according to any one of 1 to 5. 7. A permanent magnet having magnetic poles having polarities different from each other on a surface facing the toner carrier and a surface facing the external magnet is attached to the layer thickness regulating blade. The developing device according to claim 1. 8. A layer thickness regulating blade made of a non-magnetic material is provided in place of the layer thickness regulating blade made of a magnetic material.
3. The developing device according to claim 1.